Low halide lanthanum precursors for vapor deposition

ABSTRACT

Lanthanide compounds for vapor deposition having ≤50.0 ppm, ≤30.0 ppm, or ≤10.0 ppm of all halide impurity combined is provided. The purification systems and methods are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.17/394,328, filed Aug. 4, 2021, which is a divisional of applicationSer. No. 16/685,266 filed Nov. 15, 2019, which is now abandoned.Application Ser. No. 16/685,266 claims the benefit of priority to U.S.provisional application Ser. No. 62/772,450 filed Nov. 28, 2018. Allapplications are hereby incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

The invention relates generally to a composition comprising lanthanidesuch as lanthanum precursors containing 10.0 ppm or less and preferably<5.0 ppm of halide impurities such as fluorine, chlorine, bromine oriodine. The invention also relates to the method for deposition oflanthanum-containing films, such as lanthanum oxide, metal oxide dopedwith lanthanum oxide, lanthanum nitride and metal nitride doped withlanthanum nitride. Lanthanum-containing films are used in electronicindustrial applications.

Thin films of rare earth oxides are of interest because of theirpotential use as dielectrics in microelectronics applications. Inparticular, lanthanum oxide (La₂O₃) is attractive for a number ofreasons including its favorable conduction band offset at the La₂O₃/Siinterface. This and other properties have led some to consider La₂O₃ orLa-containing oxides for use as high-k materials inmetal-oxide-semiconductor field effect transistors (MOSFETs) andcapacitive devices. La₂O₃ has found use as a “capping layer” to adjustwork functions in advanced MOSFETs.

Lanthanide complexes, such as lanthanum cyclopentadienyl and lanthanumamidinate complexes are widely used in electronic industry as precursorsfor chemical vapor deposition or atomic layer deposition oflanthanum-containing films. For various applications, semiconductorindustry requires high purity precursors with trace metals and halideimpurities well below single ppm's for metals and lower than 10.0 ppmfor halides. This is because increasing the speed and complexity ofsemiconductor integrated circuits requires advanced processes that putextreme constraints on the level of contamination allowed on thesurfaces of silicon wafers.

Metallic and halide contaminations on wafer surface are known to be aserious limiting factor to yield and reliability of CMOS basedintegrated circuits. Such contamination degrades the performance of theultrathin SiO2 gate dielectrics that form the heart of the individualtransistors. Halides impurities may migrate in the device and causecorrosion. The commonly reported mechanism for electrical fieldbreakdown failure from iron contamination is the formation of ironprecipitates at the Si—SiO2 interface, which frequently penetrate thesilicon dioxide. Halide impurities present in lanthanum precursors mayalso cause corrosion of stainless steel containers used for delivery oflanthanum containing precursors to the deposition tool and transfer ofiron and other stainless steel metal impurities to thelanthanum-containing film causing device failure.

Thus, precursors with low levels of halide contamination are highlydesired. Purification methods to produce precursors with low halidecontamination are also desired.

Commonly used precursors for deposition of lanthanum-containing filmsare lanthanum amidinates or La(AMD)₃, such as for example tris(N,N′-di-isopropylformamidinato) lanthanum (III) or La(FAMD)₃, lanthanumcyclopentadienyl complexes, such as for exampletris(isopropylcyclopentadienyl) lanthanum (Ill) or La(iPrCp)3, andlanthanum diketonate complexes. Most common preparation of suchlanthanum includes lanthanum halides as starting materials resulting inhalide contamination.

Several methods were previously considered for purification of lanthanumcompounds, for example crystallization and sublimation.

Hecker (U.S. Pat. No. 2,743,169 A) taught a sublimation method that canbe used for metal chlorides separation and purification. Typically,sublimation is operated at reduced pressure, which can enhance theproductivity and reduced operation temperature. The product is usuallyformed on a cold wall, and is harvested at the end of the purificationprocess in an inert environment, as most metal halides are air andmoisture sensitive.

For better solid product uniformity, fluidized bed is often used.Another advantage of using fluidized bed is to allow for automation ofsolid handling, which is difficult to implement with vacuum sublimationprocess. Schoener et al (U.S. Pat. No. 4,478,600) taught a method ofusing fluidization as part of aluminum chloride purification processyielding controlled product particle size. In the art, raw aluminumchloride was firstly generated through chlorination reaction at hightemperature, in vapor phase, followed by a condensing stage to removemost solid impurities. The vapor is then supplied into a fluidizationchamber to form product particles. Non-condensable contents, such aschlorine, carbon dioxide, and fluidizing gas are passed through acooling fin for temperature control. Part of the gas is recycled by apump, whereas the rest is vented through a scrubber. In this work, coldfluidization zone is provided for product condensation and particleformation.

Thus, the objective of this invention is to provide lanthanidecyclopentadienyl or lanthanide amidinate complex containing less than10.0 ppm of chloride, bromide and fluoride, preferably less than 5.0 ppmhalide, and more preferably less than 1.0 ppm halide.

Another objective of this invention is to provide lanthanideformamidinate or La(FAMD)₃ containing 50.0 ppm or less, 30.0 ppm orless, 20.0 ppm or less, 10.0 ppm or less, 5.0 ppm or less, or 2.0 ppm orless of all halide compounds combined.

Another objective of this invention is to provide a practical andscalable method for production of low halide lanthanide formamidinate.

BRIEF SUMMARY OF THE INVENTION

Accordingly, the present invention provides a low halide composition; amethod and a system to purify a crude material comprising lanthanideamidinates, or more specifically lanthanum amidinate compounds to obtainthe high purity composition comprising lanthanum amidinate compounds,and a delivery system to deliver the high purity composition comprisinglanthanide amidinate compounds.

In one aspect, there is provided a lanthanide amidinate compoundLn(AMD)₃ having Formula I

-   -   wherein R¹ is selected from the group consisting of hydrogen,        and C₁ to C₅ linear or branched alkyl; R² and R² are        independently selected from the group consisting C₁ to C₅ linear        or branched alkyl; Ln is a lanthanide selected from the group        consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,        Tm, Yb, Lu;    -   the lanthanide amidinate compound comprises at least one halide        impurity selected from the group consisting of chloride,        bromide, fluoride, iodide and combinations thereof; wherein each        of halide impurity ranges from 10.0 ppm or less, 5.0 ppm or        less, 2.5 ppm or less, or 1.0 ppm or less; and all halide        impurity combined ranges 50.0 ppm or less, 30.0 ppm or less,        20.0 ppm or less, 10.0 ppm or less, 5.0 ppm or less, or 2.0 ppm        or less by weight.

The halide impurity comprises fluoride, chloride, iodide and/or bromide.The halide impurity forms volatile compounds that are deposited onto thefilm and have a negative effect on the dielectric constant.

In another aspect, there is provided practical and scalable method forproduction of high purity Lanthanide amidinate compounds; comprising

-   -   a. providing the crude lanthanide amidinate material comprises        lanthanide compound having Formula I

-   -   -   wherein R¹ is selected from the group consisting of            hydrogen, and C₁ to C₅ linear or branched alkyl; R² and R²            each is independently selected from the group consisting of            C₁ to C₅ linear or branched alkyl; and Ln is a lanthanide            selected from the group consisting of La, Ce, Pr, Nd, Pm,            Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; and        -   the crude lanthanide amidinate material comprises at least            one impurity selected from the group consisting of (i)            halide impurities selected from the group consisting of            LnCl_(x)(AMD)_(y) (x+y=3), LnBr_(x)(AMD)_(y) (x+y=3),            LnF_(x)(AMD)_(y) (x+y=3), LnI_(x)(AMD)_(y) (x+y=3), wherein            x or y is selected from 1 or 2, and combinations            thereof; (ii) light impurity LnO(AMD)₂, and (iii) trace            metals, and (iv) trace amounts of non-volatile impurities            Ln₂O₃, Ln(OH)₃, or combinations;

    -   b. providing zone 1 comprising at least one sublimer, zone 2        comprising at least one condenser; and zone 3 comprising at        least one cooler; optionally a separation unit installed between        zone 1 and zone 2 and selected from the group consisting of        convoluted pathway, glass wool, filter, and combinations        thereof; wherein zone 2 is in fluid communication with zone 1        and zone 3 is in fluid communication with zone 2;

    -   c. heating the crude lanthanum amidinate material contained in        the at least one sublimer in zone 1 to get crude lanthanum        amidinate material vapor separated from the halide impurities        and the trace amounts of non-volatile impurities;

    -   d. passing the crude lanthanide amidinate material vapor from        the zone 1 to the at least one condenser in zone 2 and        condensing the crude lanthanide amidinate material vapor to form        purified lanthanide amidinate material in the at least one        condenser;

    -   e. passing the non-condensed light impurity LnO(AMD)₂ from the        zone 2 into the at least one cooler in zone 3 to form solid        light impurity;

    -   wherein the purified lanthanide amidinate material comprises        each of halide impurity ranging from 10.0 ppm or less and all        halide impurities combined ranging from 50.0 ppm or less.

In yet another aspect, there is provided a system for purifying a crudelanthanide amidinate material for vapor deposition comprising

-   -   a) the crude lanthanide amidinate material comprises lanthanide        amidinate compound having Formula I

-   -   -   wherein R¹ is selected from the group consisting of            hydrogen, and C₁ to C₅ linear or branched alkyl; R² and R²            each is independently selected from the group consisting of            C₁ to C₅ linear or branched alkyl; and Ln is a lanthanide            selected from the group consisting of La, Ce, Pr, Nd, Pm,            Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu;

    -   b) zone 1 comprising at least one sublimer; wherein the crude        lanthanide amidinate material is placed inside the at least one        sublimer

    -   c) zone 2 comprising at least one condenser; wherein zone 2 is        in fluid communication with zone 1; and

    -   d) zone 3 comprising at least one cooler; wherein zone 3 is in        fluid communication with zone 2; and optionally

    -   e) a separation unit selected from the group consisting of        convoluted pathway, glass wool, filter, and combinations thereof        installed between zone 1 and zone 2;        -   wherein        -   the crude lanthanide amidinate material comprises 50 ppm or            more at least one impurity selected from the group            consisting of (i) halide impurities selected from the group            consisting of LnCl_(x)(AMD)_(y) (x+y=3), LnBr_(x)(AMD)_(y)            (x+y=3), LnF_(x)(AMD)_(y) (x+y=3), LnI_(x)(AMD)_(y) (x+y=3),            wherein x or y is selected from 1 or 2, and combinations            thereof; (ii) light impurities LnO(AMD)₂, (iii) trace            metals, and (iv) trace amounts of non-volatile impurities            Ln₂O₃, Ln(OH)₃, or combinations;        -   and        -   purified lanthanide amidinate material is inside the at            least one condenser in zone 2; and the purified lanthanide            amidinate material comprises each of halide impurity ranging            from 10.0 ppm or less and all halide impurities combined            ranging from 50.0 ppm or less.

In yet another aspect, there is provided a delivery system or a vesselcontaining the purified lanthanide amidinate compound as disclosed aboveas a precursor.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exemplary purification system to remove halides.

FIG. 2 is an exemplary purification system having a physical barrier(such as a filter) between raw material and purified material accordingto certain embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The method and the system described in present invention are generallyto remove impurities from Lanthanide amidinate compounds through phasechanging process.

The purified lanthanide amidinate compound Ln(AMD)₃ having Formula I

-   -   wherein R¹ is selected from the group consisting of hydrogen,        and C₁ to C₅ linear or branched alkyl; R² and R² are        independently selected from the group consisting C₁ to C₅ linear        or branched alkyl; Ln is a lanthanide selected from the group        consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er,        Tm, Yb, Lu;    -   the lanthanide amidinate compound comprises at least one halide        impurity selected from the group consisting of chloride,        bromide, iodide, fluoride and combinations thereof; wherein each        of halide impurity ranges from 10.0 ppm or less, 5.0 ppm or        less, 2.5 ppm or less, or 1.0 ppm or less; and all halide        impurity combined ranges 50.0 ppm or less, 30.0 ppm or less,        20.0 ppm or less, 10.0 ppm or less, 5.0 ppm or less, or 2.0 ppm        or less by weight.

The raw or crude lanthanide such as lanthanum material mainly comprisesup to 99.8 wt. % of primarily target lanthanide amidinate, and 1 ppm ormore, 2 ppm or more, 5 ppm or more, 10 ppm or more, 50 ppm or more,impurities including but are not limited to (i) less volatile impuritiessuch as LaCl_(x)(AMD)_(y) (x+y=3), LaBr_(x)(AMD)_(y) (x+y=3);LaI_(x)(AMD)_(y) (x+y=3); LaF_(x)(AMD)_(y) (x+y=3), wherein x and y isselected from 1 or 2; (ii) light impurities such as LaO(AMD)₂, (iii)trace metals, and (iv) trace amounts of non-volatile impurities e.g.La₂O₃, La(OH)₃, or combinations,

In general, raw or crude material is heated to certain temperature,under which lanthanide compounds are vaporized into gaseous phase in avaporization chamber. The lanthanide compound vapor is then condensedinto collecting chambers, with one of the chamber being the mainfraction collector where the pure lanthanide amidinate compounds iscollected and harvested. Non-volatile impurities are left in thevaporization chamber as heel, whereas the low boiling point lightimpurities are collected into a chamber for light impurities collection.

One aspect of preparing pure lanthanide amidinate compounds is to removeless volatile lanthanide bromides, chlorides, iodides and fluorides fromraw material. The final purified product contains 50.0 ppm or less, 30.0ppm or less, 20.0 ppm or less, 10.0 ppm or less, 5.0 ppm or less, 2.0ppm or less, or 1.00 ppm or less impurities.

According to the Thiele-McCabe method, separation of binary system atppm level requires many theoretically plates, which is not available invacuum sublimation or fluidized bed system.

Another aspect of preparing pure lanthanide amidinate compounds is toremove impurities with lower boiling point comparing to lanthanideformamidinate. These impurities can be separated through sublimation byutilizing different boiling points of product and impurities, throughproviding at least two temperature zones. Similarly, such separation canbe achieved by utilizing different vapor pressures at a fixedtemperature, and carrying low boiling impurities away with inert gas. Byproviding the suitable amount of inert gas, the Ln impurity can be keptin gaseous phase while most Ln(FAMD)₃ can be condensed, and, henceachieving separation.

Yet another aspect of this invention is to prevent product contaminationwith trace amounts of non-volatile impurities accumulated in sublimationheels. Filter media is used to filter vapor of amidinate compound fromtrace amounts of less volatile solid particulates which can be carriedover into lanthanum from amidinate vapor by dusting or other mechanism.Other metal and halide impurities may also be carried over by the samemechanism.

In most embodiments, a purification system comprises of three seriesconnected chambers: a sublimer where the raw material is vaporized, acondenser where the product is collected, and a cooler where the lightimpurity is collected.

Crude or raw lanthanide amidinate compound, which typically has 70-99.5wt. % of lanthanide amidinate compound balanced with other impurities,is loaded in the sublimer, and heated to vaporize lanthanide amidinatecompound. The vapor is passed through a heat traced connecting pipe intothe condenser. lanthanide amidinate vapor is cooled down in condenser toform product. The light impurity, in vapor phase, is further passedthrough a heat traced connecting pipe to enter the cooler, and is cooleddown and condensed in the cooler.

In certain embodiments, the vapor is forced to pass through chambers byapplying vacuum. In certain embodiments, the vapor is forced to passthrough chambers by inert gas flow. Yet in certain embodiments, bothvacuum and inert gas flow can be applied simultaneously to force thevapor flow.

In certain embodiments, the product and light impurities are condensedby cold surfaces. In other embodiments, the product and light impuritiesare condensed by cold inert gas. When condensed by cold inert gas, thecondenser can be made into a fluidized bed so the product condensed inthe gas stream can be nucleation seed and grow. By controlling theresidence time in fluidized bed, uniformed product particle size anduniformed solid product purity can be achieved.

In all embodiment, a separation unit or particle trapper including butis not limited to convoluted pathway, glass wool, filter (such as amediated filter), and combinations thereof; can be installed in thepassage entering the condenser.

In certain embodiments, the chambers of the purification system aremaintained at fixed temperature. In other embodiments, some chambers mayvary temperature during purification process, to allow for betterseparation of light impurities.

Any of the above features can be combined with any of one or more otherfeatures. Other advantages, novel features, and uses of the presentdisclosure will become more apparent from the following detaileddescription of non-limiting embodiments when considered in conjunctionwith the accompanying drawings, which are schematic and which are notintended to be drawn to scale or to exact shape. In the figures, eachidentical, or substantially similar component that is illustrated invarious figures is typically represented by a single numeral ornotation. For purposes of clarity, not every component is labeled inevery figure, nor is every component of each embodiment shown whereillustration is not necessary to allow those of ordinary skill in theart to understand the invention.

An example of the present invention is shown in FIG. 1 .

In some embodiments, the purification system 100 shown in FIG. 1comprises at least one sublimer (101), at least one condenser (104), andat least one cooler (105).

The sublimer (101) is filled with raw amidinate compound material(201A). The sublimer is heated to a predetermined temperature, cause theraw material to vaporize and generate raw material vapor (202). Thevapor is then enters the condenser (104) for product (204) collection.The none-condensed light impurity (205) is then passed into the cooler(105), and condensed there for forming solid light impurity (205).

Another example of the present invention is shown in FIG. 2 .

In some embodiments, the purification system 100A shown in FIG. 2comprises at least one sublimer (101), at least one mediated filter(103), at least one condenser (104), and at least one cooler (105).

The sublimer (101) is filled with raw amidinate compound material(201A). The sublimer is heated to a predetermined temperature, cause theraw material to vaporize and generate raw material vapor (202). Thevapor is then directed through a heat traced pipe (106), passed througha mediated filter (103) which serves as a physical barrier between rawmaterial and purified material, and then enters the condenser (104) forproduct (204) collection. The none-condensed light impurity (205) isthen passed into the cooler (105), and condensed there for forming solidlight impurity (205).

In some embodiments, the purification system 100 or 100A is operatedunder vacuum. The system can be connected to a vacuum source for suchpurpose (not shown).

In other embodiments, the purification system 100 or 100A is operatedusing carrier gas, and is under slight positive pressure. This can bedone by supplying an inert gas, such as N2, to the system (not shown).

Yet in other embodiments, the purification system 100 or 100A isoperated under vacuum and using carrier gas, as vacuum and carrier gascan be supplied to the system at the same time.

In some embodiments, the product vapor supplied to the condenser iscooled by condenser surface. In other embodiments, the product vaporsupplied to the condenser is cooled by a stream of cold inert gas (121)(not shown). Furthermore, the cold inert gas stream can be introducedthrough a distribution plate to form fluidized bed. Either way, thepurified product (204) is collected in the condenser.

In some embodiments, the light impurity vapor (205) can pass thecondenser by maintaining the condenser at high temperature at thebeginning of the process, i.e., the same temperature as the sublimer.Once all the light impurities have been vaporized and passed through thecondenser, the condenser temperature is reduced to cumulate product.

In other embodiments when cooling gas is used to condense the product,the condenser temperature can be maintained at a fix level under whichthe impurity vapor pressure is higher than the impurity concentration inthe gaseous phase, and hence no impurity will condense in the condenser.

In some embodiments, the impurity vapor (205) supplied to the cooler iscooled by cooler surface. In other embodiments, the impurity vaporsupplied to the cooler is cooled by a stream of cold inert gas (122)(not shown). Either way, the light impurity (205) is collected in thecooler.

In some embodiments, deep vacuum (<1 torr abs) is used for operation.The typical operation temperature for Zone 1 (see FIG. 1 ) is between60° C. to 200° C., between 100° C. to 180° C., or between 120° C. to160° C. The typical startup operation temperature for Zone 2 is between80° C. to 200° C., between 100° C. to 180° C., or between 120° C. to160° C., to remove the light impurities. After the light impurities areremoved, the typical operation temperature for Zone 2 is between 20° C.to 100° C., 20° C. to 80° C., or between 20° C. to 60° C. The typicaloperation temperature for zone 3 is below 30° C. at any given time.

In some embodiments, fluidized bed is used in condenser for better solidproduct uniformity. One key element to achieve the above mentioned yieldand economic aspect is to control the ratio of inlet fluidizing gas tothe inlet amidinate compound vapor at the bottom of the condenser. It isimportant to keep the ratio low, so carryover or product by the gas islimited. Since this gas stream is also a cooling source for the inletvapor, there is a lower limit for the ratio according to mass and heatbalance. In general, the fluidizing gas will be heated majorly by thelatent heat released from crystallization. Ideally, in the abovementioned temperature ranges, and ambient temperature N₂ gas is used.

Yet another key to achieve good crystal growth and high yield is to feedthe condenser with high concentration of vapor. This can be achieved byproviding high temperature to the sublimer, or limiting the carrying gassupplied to the sublimer. Combination of both options is preferred. Inoperation, it is preferable to keep the carrying gas to vapor boil upratio to be <10:1, preferable <5:1, and more preferable <2:1, in molarunit. The sublimer should be heated to the upper limit mentioned above,depending on the operation pressure. That way, with high vaporconcentration in the feed, less process residence time is achieved forthe same amount of raw material, leading to less carryover of materialas the total amount of gas passed through is reduced. In anotherembodiment lanthanide formamidinate is dissolved in inert solvent andthe solution is eluted via adsorbent bed filled with inert adsorbentwith high affinity for halide. Solvent is removed from purifiedlanthanide formamidinate and lanthanide formamidinate is furtherpurified by the methods described above.

In certain embodiments, delivery systems or vessels are provided fordepositing lanthanide-containing film comprises lanthanidecyclopentadienyl or lanthanide amidinate complex containing <10.0 ppm,preferably <5.0 ppm and more preferably <2.5 ppm of Br; and <20.0 ppm,preferably <10.0 ppm of all halide impurity combined.

The vessel may be connected to deposition equipment known in the art byuse of a valved closure and a sealable outlet connection.

Most preferably, the vessels may be constructed of high puritymaterials, including stainless steel, glass, fused quartz,polytetraflurorethylene, PFA®, FEP®, Tefzel® and the like. The vesselsmay be sealed with one or more valves. The headspace of the vessel ispreferably filled with a suitable gas such as nitrogen, argon, helium orcarbon monoxide.

EXAMPLES Example 1 Vacuum Sublimation with Raw Lanthanum FormamidinateLa(FAMD)₃ Having R¹ Hydrogen, R²=R³=Iso-Propyl Using Purification System100

The purification system 100 shown in FIG. 1 was used.

600 gram of raw lanthanum formamidinate La(FAMD)₃ material was purchasedfrom Strem Chemicals Inc., 7 Muliken Way, Newburyport, MA and placedinto the sublimer 101. The halides and trace metals in the raw materialwere measured by Ion chromatography (IC) and were listed in Table I.

The system was evacuated to <0.5 torr abs pressure.

The sublimer was heated to 70° C. The condenser was heated to 70° C. forthe first 5 hours. After 5 hours the sublime was heated to 160° C. andthe condenser was run at room temperature (RT 20 to 25° C.) where theamidinate compound was condensed. The cooler was maintained at roomtemperature all the time

TABLE I Raw Purified La(FAMD)₃ Assay 99.7 wt. % 99.9 wt. % Chloride  5.7ppm  1.8 ppm Bromide 583 ppm 19.8 ppm Li [No Gas] 0.01 0.01 Na [No Gas]0.05 0.04 Mg [No Gas] 0.01 0.01 Al [No Gas] 0.01 0.01 K [H2] 0.08 0.1 Ca[H2] 0.01 0.13 Ti [No Gas] 0.01 0.01 Cr [H2] 0.02 0.03 Mn [No Gas] 0.010.01 Fe [H2] 0.02 0.06 Co [No Gas] 0.01 0.01 Ni [No Gas] 0.01 0.01 Cu[No Gas] 0.01 0.02 Zn [No Gas] 0.01 0.07

The process was stopped after 24 hours.

197 gram of product was collected.

The halides and trace metals in the product were measured by Ionchromatography (IC), and listed in Table I.

The results indicated that sublimation reduced halide contents. However,chloride was around 1 ppm and bromide concentration was above 50 ppm.

The results also showed that the system was not efficient to reducetrace metals. Please notice the low level of the trace metals initiallycontained in the raw material.

Example 2 Vacuum Sublimation of Raw Lanthanum Formamidinate La(FAMD)₃Having R¹=Hydrogen, R²=R³=Iso-Propyl Using Purification System 100A

The purification system 100A shown in FIG. 2 was used.

193 grams of raw La(FAMD)3 material was purchased from Strem ChemicalsInc., 7 Muliken Way, Newburyport, MA and placed into sublimer. Thehalides and trace metals in the raw material were measured by Ionchromatography (IC) and were listed in Table 2.

TABLE II Raw Product La(FAMD)₃ Assay 99.72% 99.8% Chloride  5.7 ppm 0.9ppm Bromide 563.8 ppm 1.0 ppm Li [No Gas] 0.01 0.01 Na [No Gas] 2.190.04 Mg [No Gas] 0.05 <0.03 Al [No Gas] 0.09 0.03 K [H2] 0.08 0.04 Ca[H2] 0.14 <0.08 Ti [No Gas] <0.03 <0.03 Cr [H2] 0.09 0.02 Mn [No Gas]0.01 0.01 Fe [H2] 0.4 0.07 Co [No Gas] <0.02 <0.02 Ni [No Gas] <0.03<0.03 Cu [No Gas] 0.05 0.02 Zn [No Gas] 0.06 <0.05

A glass coarse fritted disc with porosity 40-60 micron was purchasedfrom Chemglass Life Science LLC, 3800 N Mill Rd, Vineland, NJ 08360 andused as the mediated filter 103.

The system was evacuated to <0.5 torr abs pressure.

The sublimer was heated to 140° C. The filter was heated to 200° C. Thecondenser was heated to 140° C. for the first 24 hours, and then reducedto room temperature where the amidinate compound was condensed. Thecooler was maintained at room temperature all the time.

The process was stopped as the filter clogged the passage, usually after48 hours.

40 grams of product was collected. The halides and trace metals in theproduct were measured by Ion chromatography (IC) in Table II.

The results indicated that chloride was effectively removed below 1 ppmby using system described in FIG. 2 and bromide was reduced to 1 ppm aswell.

The results also showed that there was a consistency of the reduction ofthe trace metals, considering the low level of the trace metalsinitially contained in the raw material. The system used in this examplewas more effective to reduce the trace metals.

While the principles of the claimed invention have been described abovein connection with preferred embodiments, it is to be clearly understoodthat this description is made only by way of example and not as alimitation of the scope of the claimed invention.

1. A composition comprising lanthanide amidinate compound Ln(AMD)₃having Formula I

wherein R¹ is selected from the group consisting of hydrogen, and C₁ toC₅ linear or branched alkyl; and R² and R² each is independentlyselected from the group consisting of C₁ to C₅ linear or branched alkyl;Ln is a lanthanide selected from the group consisting of La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; wherein the compositioncomprises at least one halide impurity and each of halide impurityranges from 10.0 ppm or less; and all halide impurities combined ranges50.0 ppm or less.
 2. The composition of claim 1, wherein the at leastone halide impurity is selected from the group consisting of chloride,bromide, fluoride and combinations thereof; and each of halide impurityranges from 5.0 ppm or less.
 3. The composition of claim 1, wherein thecomposition comprising ≤1.0 ppm chloride, ≤1.0 ppm bromide, and ≤1.0 ppmfluoride.
 4. The composition of claim 1, wherein R¹ is hydrogen and thelanthanide amidinate compound is selected from the group consisting ofLa(FAMD)₃, Ce(FAMD)₃, Pr(FAMD)₃, Nd(FAMD)₃, Pm(FAMD)₃, Sm(FAMD)₃,Eu(FAMD)₃, Gd(FAMD)₃, Tb(FAMD)₃, Dy(FAMD)₃, Ho(FAMD)₃, Er(FAMD)₃,Tm(FAMD)₃, Yb(FAMD)₃, and Lu(FAMD)₃.
 5. The composition of claim 1,wherein the lanthanide is lanthanum and R¹ is hydrogen.
 6. A vesselcontaining a composition comprising lanthanide amidinate compoundLn(AMD)₃ having Formula I

wherein R¹ is selected from the group consisting of hydrogen, and C₁ toC₅ linear or branched alkyl; and R² and R² each is independentlyselected from the group consisting of C₁ to C₅ linear or branched alkyl;Ln is a lanthanide metal selected from the group consisting of La, Ce,Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu; wherein thecomposition comprises at least one halide impurity and each of halideimpurity ranges from 10.0 ppm or less; and all halide impuritiescombined ranges 50.0 ppm or less.
 7. The vessel of claim 6, wherein theat least one halide impurity is selected from the group consisting ofchloride, bromide, fluoride and combinations thereof; and each of halideimpurity ranges from 5.0 ppm or less.
 8. The vessel of claim 6, whereinthe lanthanide amidinate compound is selected from the group consistingof La(FAMD)₃, Ce(FAMD)₃, Pr(FAMD)₃, Nd(FAMD)₃, Pm(FAMD)₃, Sm(FAMD)₃,Eu(FAMD)₃, Gd(FAMD)₃, Tb(FAMD)₃, Dy(FAMD)₃, Ho(FAMD)₃, Er(FAMD)₃,Tm(FAMD)₃, Yb(FAMD)₃, and Lu(FAMD)₃.
 9. The vessel of claim 6, whereinthe lanthanide is lanthanum and R¹ is hydrogen.
 10. The vessel of claim6, wherein the composition comprising ≤1.0 ppm chloride, ≤1.0 ppmbromide, and ≤1.0 ppm fluoride.